One of conventional apparatus for writing a line on a patterned substrate comprises a laser light source for radiating a laser beam, a CVD (Chemical Vapor Deposition) cell having a window through which the laser beam is passed, an inlet through which vapor of CVD raw material gas is supplied, and an outlet to which an exhaust gas treatment unit is connected, and an X-Y stage on which the CVD cell is provided.
In operation, a substrate having a surface which is patterned by different materials is positioned, and the CVD raw material gas is supplied through the inlet into the CVD cell. At the same time, the laser light source is driven to radiate the laser beam which is focussed to pass through the window of the CVD cell so that the substrate is subject to the radiation of the laser beam therein. In the CVD cell, the CVD raw material gas is thermally decomposed due to a reaction at the interface of the gas and substrate so that a predetermined pattern of a line is deposited with the decomposed gas on the substrate in accordance with the scanning of the laser beam thereon.
The above mentioned operation is described, for instance, on pages 957 to 959 of "Appl. Phys. Lett. 39(12), Dec. 15, 1981" and on page 32 to 35 of "IEEE ELECTRON DEVICE LETTERS, VOL. EDL-5, NO. 2, February 1984".
In the former, a Si wafer from which a thermal oxidation film of SiO.sub.2 is partially removed is positioned in a gas atmosphere of SiH.sub.4, while Ar-ion laser beam scans the Si wafer to be heated up to a predetermined temperature. As a result, the SiH.sub.4 gas is thermally decomposed so that a direct writing of Si can be performed on the Si wafer.
In the latter, a CMOS chip is subject to the radiation of Ar-ion laser beam to be formed with boron-doped poly-Si thereon so that a contact can be formed between the boron-doped poly-Si and Al wiring, thereby modifying an erroneous wiring in the CMOS chip.
According to the conventional apparatus for writing a line on a patterned substrate, however, there are resulted following disadvantages.
First of all, it is difficult to write a well defined thick line on a substrate in an expected high speed operation. This is why a radiation pattern of a laser beam is of a circular beam having Gaussian intensity distribution so that the scanning speed must be very high to shift the radiation position on the substrate prior to the occurrence of the thermal spread so as to provide a narrow width of a line thereon. Due to the high speed scanning of the laser beam, a thick line having a low wiring resistance can not be obtained.
Secondly, there is liable to be resulted an undesirable thinner line on the substrate when the scanning speed of a laser beam is increased without varying a power of the laser beam. In order to avoid the phenomenon, if the scanning speed of a laser beam is increased simultaneously with the increase of a radiation power of the laser beam, the center portion of a line is damaged due to an excessive thermal energy, and a line is transversely spread so that a width thereof is larger than a specified line because a region in which a raw material gas is thermally decomposed is transversely enlarged. In order to allow the increase of the scanning speed of a laser beam, further, it is considered that a supply amount of the raw material gas must be increased. In such a case, a film quality of a line is deteriorated to result in the increase of the resistivity thereof. For these reasons, it is difficult to write a line on a substrate in a high speed without decreasing characteristics of a film quality, thickness, and width thereof.
Thirdly, there is resulted a disconnection of a line or thinner line when the writing of a line is performed on a step portion of the substrate in a case where a minimum step moving distance of a scanning stage is nearly equal to a spot size of a laser beam so that an area on which the laser beams are overlapped in accordance with the moving of the stage is small. To avoid the disadvantage, a stage which has such a very fine minimum moving distance as sub-micron meter much smaller than a spot size of a laser beam must be adopted therein. Actually, however, it is not practical to utilize such a stage therein because the stage becomes very expensive, and the surrounding in which an apparatus for writing a line on a substrate including the stage is installed must be cared to maintain the performance thereof.
Fourthly, it is difficult to form a contact connecting a Si line to Al wiring because the thermal conductivity of Al is larger than that of such insulator films as SiO.sub.2, SiN etc. by one figure. In more detail, even if the Al wiring is subject to the radiation of Ar-ion laser beam, the Al wiring is not heated up to a predetermined temperature by which a CVD of Si can be performed so that a good quality of Si-deposition is not obtained.
Finally, a disadvantage similar to the fourth disadvantage mentioned above is observed in a contact of Si line for connecting Al wiring on the upper and lower surfaces of an insulator film or passivation film through a via hole provided thereinto which is indispensable to the formation of wiring for a multilayered LSI. In such a use, there is observed a further disadvantage that it is difficult to form the burying of Si into the via hole so as to be in contact with the Al wiring at the bottom thereof due to the bad coverage of Si lines which are written on the side wall of the via hole because it is difficult that the side wall of the via hole is directly heated up to a predetermined temperature by a laser beam.
Such disadvantages that an uniform width of a direct-write line is difficult to be obtained on a substrate having different thermal conductivities by a laser CVD, that a good quality contact with Al wiring is difficult to be obtained, and that a deposition material is difficult to be buried into a via hole with a predetermined characteristic so that a good quality of a contact with Al wiring at the bottom of the via hole is difficult to be formed are occured not only in Si as mentioned before, but also in a case where one of CVDs of Mo, W, and W respectively induced from Mo(CO).sub.6, W(CO).sub.6, and WF.sub.6 is utilized.